The present invention relates generally to the time compression and expansion of electrical signals, and, more particularly, to nonlinear wave guides for signal time compression and expansion.
Fast signals with nanosecond duration pose a serious challenge for data acquisition. With the current prevalence of digital signal processing, it is usually an analog-to digital converter (ADC) in the chain of signal and data processing elements that creates a performance bottleneck. Once converted, there are abundant resources available in manipulating the data digitally for optimum results without having to worry about further degradation of the signal-to-noise ratio. Even with tremendous advances in semiconductor processing technology, commercial off-the-shelf ADCs are not quite fast enough to capture nano-second events.
ADCs with high conversion speeds based on optical sampling are being studied by various organizations but with limited success, mainly because of cumbersome and complex electro-optic components. The pace of developments in all of these ADCs, however, is slowing down as the technology matures. For a leap in performance, a fresh new technology is required.
In accordance with the present invention, nonlinear coplanar waveguide devices perform dynamic time expansion (DTE) and dynamic time compression (DTC) on fast broadband signals with nanosecond duration. DTE provides a preprocessing stage to time-expand a fast signal prior to digitizing by an analog-to-digital converter (ADC), whereas DTC provides a post-processing stage to time-compress the output of a digital-to-analog converter (DAC). DTE and DTC implementation will provide significant enhancements in detection and generation of fast signals with large bandwidths for communication and radar applications as well as in laboratory RandD environments.
Various features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
The present invention includes a system for dynamic time expansion or compression of a small-amplitude input signal that is generated with an initial time scale. A nonlinear waveguide having a variable refractive index is connected to a bias voltage source having a bias signal amplitude that is large relative to the input signal to vary the refractive index and concomitant speed of propagation of the nonlinear waveguide and an electrical circuit for applying the small-amplitude signal and the large amplitude bias signal simultaneously to the nonlinear waveguide. The large amplitude bias signal with the input signal alters the speed of propagation of the small-amplitude signal with time in the nonlinear waveguide to expand or contract the initial time scale of the small-amplitude input signal.